⚡ DOWNSTRIKE

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Downstrike — the weather word for a lightning bolt that hits the ground. A live lightning map centered on your home. No accounts, no sign-ups: everything runs in your browser, using free public data.

01 · How the lightning is tracked

Strikes come from Blitzortung.org, a worldwide network of radio receivers run by volunteers. Nobody points a camera at the sky — the network hears every bolt and finds it with a stopwatch:

A lightning bolt is a radio transmitter. Its huge burst of electric current sends out a radio pulse that travels thousands of kilometres at the speed of light. (It's the crackle you hear on AM radio during a storm.)
Volunteers listen at home. Each station is a small antenna kit with a GPS clock accurate to a millionth of a second, which records the exact moment the pulse arrives.
Timing finds the bolt. Radio travels about 300 metres every microsecond, so stations farther away hear the pulse a little later. Compare arrival times at four or more stations and the possible locations cross at one point: the strike. It's GPS in reverse — many receivers timing one flash to find it.
Usually 20–40 stations hear each strike, pinning it to about a kilometre. It reaches your screen 5–15 seconds after the real flash.

Downstrike keeps a live connection to this feed and receives every located strike on Earth — often 50+ per second. Because it's a volunteer network, a strike is occasionally missed or placed a kilometre or two off. The data is free for personal use.

Why doesn't the map show every flash I see? When a storm is overhead, your eyes will always win. Most lightning never touches the ground — it jumps between clouds, lighting up the whole sky but whispering on the radio, so the network can rarely pinpoint it. One flickering flash can also be several strokes down the same channel, which the map draws as a single dot. And on a dark night you can see the glow of storms more than 100 km away. The dots you see are the bolts the network could pinpoint — mostly the powerful ones that hit the ground. If the map shows a storm, the storm is real; your eyes just see the fireworks the radios can't catch.

02 · What's on the map

Strike dots. A new strike lands with a white flash, then cools like an ember — the color tells you its age:

now
2 min
8 min
16 min
30 min, then gone
So a storm paints its own trail: white at the front, embers behind.
Thunder rings. Each strike sends out a ring growing at 343 m/s — the real speed of sound. When a ring crosses your house, that's the exact moment you'd hear the rumble.
Home rings. Dashed circles at 10, 25 and 50 km show distance at a glance. The amber glow on the outer ring points toward recent strikes and brightens as a storm gets closer.
WIND. Hundreds of particles drift with the real wind (live data, refreshed every 30 minutes).
RADAR. Live rain radar, refreshed every 5 minutes, off by default. (The free tiles get blurry if you zoom way in.)

03 · The thunder sound

The thunder is generated live by code — no recordings — and shaped by the strike's real distance, the same way air shapes real thunder:

Layer	What it is	When you hear it
Boom	A deep, blunt impact with an echo	Only within ~12 km — harder the closer the strike
Sub-bass thump	A low 50 Hz punch you feel	Within ~25 km
Rumble	A rolling growl with random peaks	Always — it's all that's left of a far-away strike

The farther the strike, the quieter it gets (about 10× softer by 50 km), the deeper it sounds (air soaks up the high notes first), and the longer and slower it rolls. Flip SOUND on to hear a preview — browsers need one click on the page before they'll play audio.

04 · The controls

The top strip. One line with the essentials — closest strike, strikes per minute, wind, and rain. Tap it to open the full detail cards.
The icon row. Radar and wind toggle those layers. The house brings you back home (press it at home to change your address), and the sliders icon opens Settings — home of the alert distance (5–50 km; any strike inside it fires the red banner and thunder at that strike's real distance), the thunder sound switch, and — in the iOS app — storm warning notifications.
The big glowing bolt is ⚡ STORM — our favorite button, so it's the big one. One press flies you to the most active storm on Earth right now; press again to hop to the next. Away from home, you hear what you'd hear standing at the crosshair in the middle of the screen: any strike inside its dashed 50 km ring plays at its real distance.
ALERTS (iOS app). Turn it on and your phone gets a push notification when the National Weather Service issues a severe thunderstorm or tornado warning for where you are — even with the app closed. These are the official warnings, checked every few minutes.
Next hour rain (iOS app). A minute-by-minute strip showing when rain will start and stop at your location over the coming hour, powered by  Weather.

05 · Privacy & sources

Your address is looked up once and saved only in your browser. No accounts.

Visits to the website are counted with GoatCounter, a privacy-friendly counter that uses no cookies and collects no personal data. The iOS app contains no analytics at all.

One exception, and only if you turn on ALERTS in the iOS app: your device's push token and your location rounded to about a kilometre are stored on our server, because something has to check the warnings while your phone is asleep. Nothing else is stored, and turning ALERTS off deletes that record. Full details in the privacy policy.

One more honest note: Downstrike is for learning and storm-watching fun. It is not an emergency service — in dangerous weather, follow official guidance.

What	Source	Cost
Lightning strikes	Blitzortung.org community network	Free (personal use)
Basemap	CARTO dark-matter · OpenStreetMap	Free
Wind	Open-Meteo	Free
Rain radar	RainViewer	Free (zoom-limited)
Geocoding	OSM Nominatim	Free, used once
Visit counter (website)	GoatCounter (no cookies)	Free
Storm warnings (iOS)	National Weather Service	Free
Rain nowcast (iOS)	Apple Weather / WeatherKit	Free

06 · Credits

Downstrike was designed and created by Leo and Noah Zimmerman, with help from Claude. Strike data flows thanks to the volunteers of the Blitzortung.org network.